A clear distinction has traditionally been made between wireless and wireline services, as well as between access networks providing these services.
Typical examples of wireless services are the voice services provided by cellular mobile networks and the radio and TV broadcast services provided by the broadcast networks One characteristic of these networks is that they provide almost ubiquitous access to the services, i.e. almost full coverage. The quality of the service is directly related to the quality of the radio signal received by the users, hence the radio signal quality is an important performance parameter used by the service provider when deploying and operating the access network.
Typical examples of wireline service are landline telephony, typically provided by twisted pair copper connections, and cable TV, typically provided by coaxial cables. Development of digital technology during the last decades have allowed for the provided services to be distinguished from the technology used by the underlying access network. Thus, customers may nowadays be offered a bundle of telephony, TV and internet access, irrespective of the physical type of connection.
From the end user perspective, the distinction between wireless and wireline realms may become less clear due to two reasons. First, the connection to a wireline network may often be done by means of a radio interface, such as a Digital Enhanced Cordless Technology (DECT) network in case of a phone, or a Wireless Local Area Network (WLAN) connection in the case of internet access. Second, similar services are provided by both wireless and wireline access networks, such as internet access or TV programs. For instance, a phone connection using the application Skype on a Personal Digital Assistant (PDA) over a WLAN may give a rather similar experience to a phone connection over a cellular network, although the underlying technology and the business models may be completely different. An important difference is that the quality of the cellular connection is monitored and guaranteed by the mobile operator, while the WLAN is a user deployed extension of a wireline access network for which the service provider has no responsibility.
A further aspect that blurs the distinction between the wireless and the wireline realms is that many cellular terminals or user equipments have the necessary interfaces to also connect to a WLAN. Thus, the user equipment may route its data through a wireline access network instead of the cellular access network. In most of the cases, the user equipment is logically connected to a network that is distinct from the cellular network, e.g. it receives a new or separate Internet Protocol (IP) address. However, in other cases the WLAN may be deployed by the mobile operator and incorporated into the mobile network. Thus, the mobile network retains the logical control over the user equipment, the access network behind the WLAN connection is integrated into the mobile network and the connection to the WLAN may be seen as a handover between different access technologies.
The mobile, i.e. wireless, and the fixed, i.e. wireline, networks are expected to merge in the future from a physical, logical, and business point of view, so that the end user may seamlessly take benefit of both types of infrastructures. Nonetheless, this fixed mobile convergence might not be relevant for all the operators, as some operators may continue to own only one type of access network and provide only wireless, respectively only wireline, access services even in the future.
A clear distinction has traditionally been made between user deployed and operator deployed wireless networks. In the former case, the customer typically takes full responsibility for the acquisition of the equipment, and for the network deployment and operation. The equipment is of consumer electronics type, and the network is operated in unlicensed bands. A typical example is the family of products and networks based on the Institute of Electrical and Electronics Engineers (IEEE) standards.
In the latter case, an operator acquires the equipment, deploys the infrastructure and has responsibility for the network operation. The contact between the operator and customer is based on contracts including service level agreements. The wireless access network is typically operated in licensed bands, and the access equipment, i.e. base station, is typically not of consumer electronics type. A typical example is the family of products and network based on the Third Generation Partnership Project (3GPP) standard.
The distinction between user deployment and operator deployment becomes less clear with the introduction of new products, such home relays/repeaters and home base stations (HBS), also referred to as femto base stations or Home (e)NodeB (H(e)NB). These devices operate in licensed bands, often on the same carrier that is used by macro base stations for outdoor coverage. Nonetheless, the installation and exact placement of these devices are left to the customers, quite similar to the case of user deployed networks, and the operation of these devices is often shared between the customer and the macro base station operator.
As of today, devices like home base stations are not sold through retail markets as regular consumer products, but they may be purchased from the operators. Alternatively the operator is offering its customers leased or subsidized devices.
Home base stations or femtos are small base stations, typically designed for use in a home or small business. For a mobile network operator, the main attraction of the home base stations are improvements to both coverage and capacity, especially indoors, where some users may experience bad performance from the macro network.
These home base stations are operating in the licensed spectrum, using one of the typical mobile communications standards, such as Wideband Code Division Multiple Access (WCDMA), High Speed Packet Access (HSPA), Code Division Multiple Access (CDMA) 2000 or Worldwide Interoperability for Microwave Access (WiMax), and are currently under standardization for Long Term Evolution (LTE) in 3GPP.
The home base stations are not directly connected to the core network by means of a backhaul link which is part of the mobile network, but via a broadband connection, such as Digital Subscriber Line (DSL) or cable, in the home. Furthermore, the operator has only very limited control, if any at all, of where the home base station is installed inside the customer's premises, and of how the home base station is operated.
Two other traditional cellular indoor solutions are based on pico base stations and on distributed antenna systems, respectively. Pico base stations implement exactly the same interfaces, protocols, and algorithms as a macro base station, but has lower dimensions, lower transmitted power, and lower processing capabilities. The operator may deploy one or several pico base station(s) in a building, each of them providing service in a limited area.
Distributed antenna systems refer to a specific type of antenna system in which many antenna elements, e.g. radio heads, are connected to the same feeder but physically located in different places in a building. The feeder of this type of antenna system is connected to one or several base stations, typically located somewhere in the building.
From an architectural point of view, there is no difference between a pico base station, or a distributed antenna system, and a macro base station. They are all deployed and managed by the operator, and the connection to the wireless access network is done through backhaul connections installed and managed by the operator.
The deployment of home base stations should be performed in a way such that the quality of the mobile service provided to the customers is improved in the best possible way, but at a minimal cost for the mobile operator.
Since the home base stations are usually offered as a subsidized device, and therefore comes at a cost for the operator, the decision where to deploy home base stations is an important one.
There are two current deployment alternatives, in which the operator does not take an active role. In the first alternative, which is the one most commonly used today, the operator may passively sell or lease the home base stations to the customers interested in having them. In the second alternative, home base stations may be dispatched to those customers that contact the operator to complain about poor indoor services.
Although the home base station may function in open access mode, that is allowing user equipments to connect to it just like any macro base station, the main scenario considered for the home base station is to handle Closed Subscriber Groups (CSG). Thus, each home base station has configured a CSG, and access is granted only to user equipments belonging to this group.
One approach is to let the owner of the home base station configure the content of the CSG. Nonetheless, the home base station currently commercialized is remotely configured by the operator upon requests from the owner of the home base station. This means that the customer effectively has no control over the CSG content.
Relaying techniques may be used to boost the quality of the radio signal, for instance when the direct radio connection between the base station and the user equipment is too weak. The most common solution is to use analog Radio Frequency (RF) repeaters, which typically receive the signal with the help of an antenna, amplifies the signal and sends it from another antenna which is radio isolated from the first antenna. This solution may be used for providing indoor coverage, for instance by mounting one of the antennas outdoors, and the other one indoors.
More advanced solutions are decoding the received signal, re-encoding it and forwarding it. This allows for the signal to be forwarded on another logical channel, since the relaying device may implement advanced radio resource management algorithms. Furthermore, base stations may implement relaying techniques so that the base station may use its radio interface to connect to the access network, instead of using a wireline backhaul or a microwave link. In this case, the base station is routing its traffic through another base station, and a part of the spectrum is used for backhauling instead of being used in the direct connections with user equipments. This approach is also called “self-backhauling”, or “in-band self-backhauling”, in order to emphasize that the base station is not connected to the access network in the conventional way.
From a protocol point of view, this may be implemented in several ways, as illustrated in FIG. 1. The top drawing illustrates a case where no relaying technique is involved. One of the user equipments 105 is directly connected to base station A BS A 107, while the other user equipment 103 is out of coverage. The middle drawing shows a solution where the base station B BS B 109 forwards the control plane channels as well as the user plane channels, i.e., acts as a traditional repeater. Hence, the user equipment 105 is logically connected to base station A 107, the existence of base station B 109 is transparent to the user equipment 105, and in effect base station B 109 only extends the coverage of cell A 111. In other words, the user equipment 105 is logically connected to base station A 107, while base station B 109 extends the coverage of cell A 111 in a transparent mode. Another approach, shown in the bottom drawing, is to let base station A 107 forward the traffic between base station B 109 and the core network. Hence the user equipment 105 is logically connected to base station B 109, which creates a new cell B 112, distinct from cell A 111. In this case, the user equipment 105 has no logical interaction with base station A 107 and is not aware of the relaying connection between base station A 107 and base station B 109. In other words, the user equipment 105 is logically connected to base station B 109, which creates a new cell B 112, distinct from cell A 111.
Although the self-backhauling architecture and the necessary protocols have been considered in the 3GPP forum only for macro base station scenarios, the idea of letting home base stations use the self-backhauling concept to connect to the access network is known and has been discussed.
In a mobile network the operator is responsible for the services delivered to the customers. The operator continuously needs to monitor the performance of the network and the services running in the network. To achieve this, the operator may use a number of methods and tools.
Traditionally the performance of the network is monitored in terms of performance of network resources or network elements. Such analysis is usually based on network element counters, which gives statistics about the performance of each network element, e.g. carried load, Central Processing Unit (CPU) usage, handover failure ratio etc. Such performance counters may either be standardized or vendor proprietary. The time granularity of network element counters are usually in the order of 5-15 minutes, and the aggregation level is usually per cell or per base station in the case of a radio network element. The output of network counter monitoring may for example serve as decision basis for where to deploy a new macro base station due to identified capacity problems in specific areas.
Another method used for network performance monitoring is to use drive tests. In this setup, special purpose user equipments are used, which are programmed to test specific aspects of the mobile network and provide detailed reports on the performance including cell level location of the measurement. This way more detailed reports on cell level may be obtained for the cells that have been visited in the drive test, but due to its nature this method does not scale up very well to handle a large network. It also does not measure the performance of real users, but of the specific test user equipments and adds additional load to the network.
It was identified in WO 2005/032186 that performance monitoring based on network element counters is not enough to understand the user perceived end-to-end quality of packet switched services in mobile networks. The document presents a system in a mobile network for monitoring the user perceived quality for individual users in the network, based on correlating traffic and mobility information extracted from passively captured traces collected from multiple standardized interfaces. In this way the end-to-end performance of individual users may be detected in the network.
Another means of getting per-user performance information is the “Subscriber and Equipment Trace” functionality specified in 3GPP, which provides very detailed information at call level on one or more specific mobile(s). Contrary to network element counters, which are permanent sources of performance information, Trace is activated on user demand for a limited period of time for a specific analysis purpose.
In a mobile network operator that already has deployed base stations for outdoor coverage, without loss of generality in the following, the coverage may be assumed to be provided by macro base stations. The macro base stations provide limited coverage also for indoor users. For instance it may provide coverage for low data rate service, such as voice and Short Message Service (SMS), but not for wireless broadband connections. The operator may own or control a wired infrastructure for providing fixed broadband access (xDSL), such as twisted pair, e.g. phone line, TV coaxial cable, optical fiber etc.
In order to improve the performance of the mobile service, particularly to enhance the service quality provided for the indoor users, the operator intends to provide home base stations to its customers.
As explained above, there are two main deployment alternatives for home base stations today, but both of these come with drawbacks. First of all, offering home base stations to all the customers may not be a good approach, due to economic reasons, for instance because the operator is subsidizing these devices or because of lack of enough devices. So the first alternative may be a costly one for the operator, and one which does not necessarily improve the indoor quality where it is best needed, but is more likely to address early adopters that may or may not experience performance problems from the macro network.
The second alternative relies on the customer actively calling the operator to complain about the bad performance. This is a risky alternative for the operator, which may result in chum of those users who simply choose to switch operator instead.
It is clear that a different approach for home base station deployment is needed so as to better enhance the overall network performance for each delivered and/or subsidized home base station.